Mesoporous oxide of titanium

ABSTRACT

This invention pertains to mesoporous oxide of titanium and processes of making mesoporous oxide of titanium particularly crystalline oxide of titanium.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of Application No.11/172,099, filed on Jun. 30, 2005 which is a continuation in part ofApplication No. 10/995,968, filed on Nov. 23, 2004 which is incorporatedhereinby reference in its entirety.

FIELD OF THE INVENTION

This invention pertains to a mesoporous oxide of titanium and processesfor making a mesoporous oxide of titanium. More particularly, the oxideof titanium is crystalline.

BACKGROUND

The control of particle microstructure is an important commercialactivity, useful, for example, in catalysis, electronics, optics,photovoltaics, and energy absorption applications. Control of particlemicrostructure allows control of physical and electronic properties, andis critical in the development of new functionalized materials. As anexample, synthesis of small particle, high surface area inorganic oxidesallows good particle dispersion in polymer binder systems for uniformcoatings with specific tailored properties, such as lightabsorption/transmittance, porosity, and durability. It is well knownthat products having attributes such as small particles, high-surfacearea, and high porosity (porosity being determined by pore volume andaverage pore diameter) can be commercially useful in many applicationsincluding, without limitation, as catalysts or catalyst supports.

Titanium dioxide is an important material because of its high refractiveindex and high scattering power for visible light, making it a goodpigment in paints and coatings that require a high level of opaqueness.TiO₂ is also active as a photocatalyst in the decomposition of organicwaste materials because it can strongly absorb ultraviolet light andchannel the absorbed energy into oxidation-reduction reactions. If theTiO₂ particles are made very small, less than about 100 nm, and if thephotoactivity is suppressed by coating the TiO₂ particles, transparentfilms and coatings can be made that offer UV protection. Therefore, TiO₂is a versatile material with many existing, as well as potential,commercial applications.

Several processes have been reported that use titanium tetrachloride,TiCl₄, as a starting source of titanium. TiCl₄ dissolved in a solvent isneutralized with a base, such as NH₄OH or NaOH, to precipitate atitanium-oxide solid that is washed to remove the salt byproducts, suchas NH₄Cl and NaCl. However, for the reaction between TiCl₄ dissolved ina solvent and NH₄OH, the inclusion of the salt byproduct, NH₄Cl, in theprecipitated solid in order to control the physical properties of thetitania product has not been known.

U.S. Pat. No. 6,444,189 describes an aqueous process for preparingtitanium oxide particles using TiCl₄ and ammonum hydroxide followed byfiltration and thorough washing of the precipitate to make a powder witha pore volume of 0.1 cc/g and pore size of 100 Å. Inoue et al. (BritishCeramic Transactions 1998 Vol, 97 No. 5 p. 222 ) describe a procedure tomake a washed amorphous TiO₂ gel by starting with TiCl₄ and astoichiometric excess of NH₄OH solution. Publication No. CN 1097400Areacts TiCl₄ with NH₃ gas in alcohol solution to precipitate NH₄Cl salt,but the titanium product is an alkoxide. A hydrated TiO₂ is made byremoving the NH₄Cl and hydrolyzing the separated liquid with water.

SUMMARY OF THE INVENTION

The disclosure relates to a process for making a mesoporous oxide oftitanium, comprising:

precipitating an ionic porogen and a hydrolyzed compound comprisingtitanium; and

removing the ionic porogen from the precipitate to recover a mesoporousoxide of titanium, the amount of ionic porogen and the conditions ofprecipitating being effective for producing a mesoporous oxide oftitanium having a pore volume of at least about 0.5 cc/g and an averagepore diameter of at least about 200 Å.

In another embodiment, the disclosure relates to a process for making amesoporous oxide of titanium, comprising:

precipitating an ionic porogen and a hydrous oxide of titanium from areaction mixture comprising a titanium starting material, a base and asolvent, wherein the titanium starting material or the solvent, or both,are a source of the anion for the ionic porogen and the base is thesource of the cation for the ionic, the precipitating being carried outunder conditions effective for recovering a mesoporous oxide of titaniumhaving a pore volume of at least about 0.5 cc/g and an average porediameter of at least about 200 Å after removing the ionic porogen fromthe precipitate.

In yet another embodiment the disclosure relates to a process for makinga mesoporous oxide of titanium, the process comprising:

forming a mixture of a solid hydrolyzed starting material comprisingtitanium and a liquid medium;

adding a sufficient quantity of a halide salt to the mixture to saturatethe liquid medium of the mixture;

recovering the solid from the saturated liquid medium, the solidcomprising a hydrolyzed intermediate comprising titanium having porescontaining the saturated liquid medium; and

removing the saturated liquid medium from the solid to recover amesoporous oxide of titanium having a pore volume of at least about 0.5cc/g and an average pore diameter of at least about 200 Å.

In one particular embodiment, a composition of matter of this disclosurecomprises mesoporous oxide of titanium having a microstructurecharacterized by a surface area of at least about 70 m²/g, a pore volumeof least about 0.5 cc/g, and an average pore diameter of least about 200Å.

In yet another embodiment, the invention relates to the use of thecomposition of matter of this disclosure as a catalyst or catalystsupport or a nanoparticle precursor. The composition of matter of thisinvention can be used in plastics, protective coatings, optical devices,electronic devices, photovoltaic cells or battery anodes, specifically,lithium-battery anodes.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 depicts a scanning electron microscope (SEM) image of calcinedpowder of Comparative Example A.

FIG. 2 depicts the X-ray powder diffraction pattern of the a product ofthe process to make TiO₂ using TiCl₄ and NH₄OH in aqueous saturatedNH₄Cl as described in Example 1.

FIG. 3 depicts a scanning electron micrograph of the product of theprocess of Example 3.

FIG. 4 depicts a scanning electron micrograph of the product formed inExample 4.

FIGS. 5 and 6 are scanning electron micrographs of the product formed inExample 5.

DETAILED DESCRIPTION

The present invention is directed to a process for forming a mesoporoustransition metal oxide of Group IVB of the Periodic Table of theElements (CAS version). Specific Group IVB transition metal oxides areTiO₂, ZrO₂, or HfO₂.

As used herein, the term “mesoporous” means structures having an averagepore diameter from about 20 upto and including about 800 Å (about 2 toabout 80 nm). The average pore diameter can, however, vary dependingupon the metal oxide and its morphology. For a crystalline oxide oftitanium the average pore diameter is at least about 200 Å (about 20 nm)and can be as high as about 500 Å (about 50 nm). More typically, thecrystalline oxide of titanium can have an average pore diameter of atleast about 200 Å (about 20 nm) up to and including about 450 Å (about45 nm).

As best shown in FIG. 5, the microstructure product of this inventioncan be a sponge-like network of Group IVB metal oxide particles. Asdescribed herein, and as shown in the scanning electron micrographs ofthe Figures, the product of this invention comprises pores, the poresbeing interstices within an agglomerate of metal oxide particles and/orcrystals.

Pore volumes and pore diameters referred to herein are determined bynitrogen porosimetry, and the surface areas are determined by BET.

The process of this invention uses a porogen. A porogen is a substancethat can create porous structures by functioning as a template for themicrostructure of the Group IVB metal oxide of this invention. Theporogen can be removed to recover a mesoporous Group IVB metal oxide.

In one embodiment of the invention, the porogen is ionic. When theporogen is ionic it can be formed in situ from the Group IVB metalcompound or the solvent, or both, and a base. The metal compound or thesolvent can function as the source of the anion for the ionic porogen.The base can function as the source of the cation for the ionic porogen.

Alternatively, an ionic porogen can be added during the process, forexample by addition of ammonium chloride to a mixture of a hydrolyzedcompound comprising Ti, Zr or Hf and a liquid medium. When the processis a continuous one, the addition of the porogen to the mixture ofhydrolyzed compound comprising Ti, Zr or Hf and liquid medium is done byany convenient method. When the process is a batch process, any methodof adding one material to another can be used.

The ionic porogen can be a halide salt. Typically, the halide salt is anammonium halide which can optionally contain lower alkyl groups. Thelower alkyl groups can be the same or different and can contain from 1upto and including about 8 carbon atoms, typically less than about 4carbon atoms. Longer chain hydrocarbons for the alkyl group of theammonium halide can be detrimental in making a calcined product becauseof charring; however, the longer chain hydrocarbons, typically over 4 upto and including about 10 carbon atoms, or even higher, would not bedetrimental in making an amorphous product. Specific examples ofammonium halides containing lower alkyl groups include, withoutlimitation, tetramethyl ammonium halide, and tetraethyl ammonium halide.The halide can be fluoride, chloride, bromide, or iodide. Even morespecifically, the halide is chloride or bromide. The ionic porogen canbe a mixture of halide salts such as a mixture of ammonium halide,tetramethyl ammonium halide and tetraethyl ammonium halide.

The porogen can be removed from the product of this invention to recovera mesoporous Group IVB metal oxide. Any suitable method for removing theporogen can be used. Contemplated methods for removing the porogeninclude washing, calcining, subliming and decomposing. It has been foundthat the choice of technique for removing the porogen depends uponwhether a substantially or completely crystalline material is desired orwhether an amorphous material is desired. When an amorphous material isdesired the porogen can be removed by washing. When a crystallinematerial is desired the porogen can be removed by volatilizing, such ascalcining.

A Group IVB metal starting material for the metal of the metal oxide isused. The Group IVB metal starting material can be a halide of a GroupIVB metal or an oxyhalide of a Group IVB metal. Specific examples ofuseful Group IVB metal starting materials include titaniumtetrachloride, titanium oxychloride, zirconium tetrachloride, zirconiumoxychloride, such as ZrOCl₂.8H₂O, hafnium tetrachloride or hafniumoxychloride, such as HfOCl₂.8H₂O. The foregoing starting materials canbe made by well known techniques. The oxychlorides can be made by mixingthe metal tetrachloride with water. The Group IVB metal tetrachloridesand the zirconium and hafnium oxychlorides are commercially available.As known to those skilled in the art titanium tetrachloride dissolved inwater forms a solution commonly referred to as titanium oxychloride.

It is believed that metal compounds containing organic groups will workin the process of this invention, however, a titanium alkoxide was foundto form mesoporous metal oxides having a pore volume and an average porediameter lower than preferred.

A hydrous metal oxide intermediate forms, from the starting material forthe metal oxide, in the presence of base or aqueous solvent, dependingupon the reaction mechanism.

A base can be used to precipitate the hydrous metal oxide intermediate.A base can also serve as the source of cations for the porogen. Suitablebases for the practice of the invention can include, without limitationthereto, NH₄OH, (NH₄)₂CO₃, NH₄HCO₃, (CH₃)₄NOH, (CH₃CH₂)₄NOH, or otherbase or mixture of bases that are removable from the product of theinvention by washing or calcining. NH₄OH is preferred.

In one embodiment of the invention, a solvent can be used in the processof this invention. A suitable solvent will depend upon the reactionmechanism, as discussed below. Solvents can be aqueous or organic,depending upon the Group IVB metal starting material. Suitable aqueoussolvents include water (when additional salt is added as discussedbelow) or aqueous halide salt such as aqueous ammonium halide. Suitableorganic solvents include lower alkyl group alcohols anddimethylacetamide. Lower alkyl group alcohols which have been found tobe particularly useful in producing metal oxides of this inventiontypically have upto and including 3 carbon atoms. Specific examples oflower alkyl group alcohols include, without limitation, ethanol,isopropanol and n-propanol. A suitable solvent can also be the aqueousor organic solvent containing dissolved halide salt (e.g., ammoniumhalide), preferably a saturated solution of halide salt.

Solvents which have a low capacity to dissolve the porogen, such asaldehydes, ketones and amines, may also be suitable solvents. Forexample, without limitation thereto, in order for ammonium halide formedin situ to precipitate and act as a porogen, organic solvents having alow capacity to dissolve the ammonium halide or the saturated aqueousammonium halide can be used.

Other examples of suitable solvents include, without limitation thereto,aqueous acid solutions, for example, a mineral acid solution. Examplesof mineral acid solutions include, without limitation thereto, solutionsof HCl, HBr or HF.

In general the suitability of a particular solvent or solvent systemwill depend upon the reactants, the porogen, the reaction mechanism andthe desired porosity of the product.

The choice of solvent will depend upon the reaction mechanism and theporosity desired. When organic solvents are mixed with aqueous reagents,such as 50 wt % TiCl₄ in water and concentrated NH₄OH, the resultingorganic-water liquid portion of the reaction mixture will dissolve moreof the porogen than would be dissolved in the organic solvent alone.However, under the conditions of this invention, enough undissolvedporogen must remain to ultimately produce a high-porosity metal-oxideproduct. A solvent in which the metal starting material is soluble istypically used.

In a specific embodiment, high porosity titanium dioxide can be obtainedby using a high level of precipitated ammonium chloride, which acts asthe porogen. This can be accomplished by performing the acid-basereaction in a solvent system having limited halide salt solubilitythereby precipitating more than about 50 wt % of the halide salt, basedon the total amount of the halide salt that can form from the reactionmixture, and especially for titanium tetrachloride, titanium oxychlorideor mixtures thereof, precipitation of more than about 70 wt % beingpreferred, and precipitation of more than about 90 wt % being mostpreferred.

In a specific embodiment of the invention, it has been found that usingsolvents with low NH₄Cl solubility can yield TiO₂ having a high surfacearea, a pore volume of about 0.5 up to and including about 1.0 cc/g, andaverage pore diameter greater than about 300 Å.

A high water concentration in the reaction mixture will reduce porevolume by dissolving water soluble porogen, thereby leaving lessprecipitated porogen available for creating pores.

Water can be introduced to the process through the source of the metalor through the source of the base: for example, when the source of themetal is in an aqueous solution or when the base is in an aqueoussolution.

It has been found that the solubility of ammonium halide in anorganic-water mixture or in saturated aqueous ammonium halide, and theinfluence of ammonium halide solubility on the porosity of the metaloxide can be affected by the form of the metal starting material. Forexample, TiCl₄ can be introduced neat, or it can be mixed with water tomake an aqueous solution which can be referred to as titaniumoxychloride solution. For this titanium oxychloride solution, as thewater:TiCl₄ weight ratio increases, ammonium halide solubility increaseswhich will result in a decrease in product porosity. Similar resultswould be obtained for aqueous solutions of base as the water:base weightratio increases.

Other solvent-specific factors can influence the pore volume of themetal oxide product; for example, different rates of precipitation ofthe porogen and the metal-oxide, and different rates of crystallizationof the porogen and the metal oxide. These factors can impact the natureof the composite precipitate and the ability of the precipitatedammonium halide to produce the high porosity metal oxide product of thisinvention.

The concentration of the metal starting material can be in the range ofabout 0.01 M to about 5.0 M, preferably about 0.05 to about 0.5 M.

The metal starting material may be in the form of a neat liquid orsolid, or, preferably, as a solution in an aqueous or organic solvent.

There are several ways in which the hydrolyzed metal compound and theporogen can be precipitated.

In one embodiment, a solvent is mixed with the metal starting materialto form a solution. The solvent-metal-halide solution is mixed with abase to precipitate the titanium and the porogen. For example withoutlimitation thereto, in the synthesis of TiO₂, titanium chloride as theneat liquid, or as an aqueous solution such as 50 wt. % TiCl₄ in waterbased on the entire weight of the solution may be mixed with thesolvent. To the solvent-titanium-chloride solution so formed is addedammonium hydroxide to precipitate the hydrous compound containingtitanium and the porogen, ammonium chloride.

In another embodiment of the invention, a solvent is first mixed withthe base. The solvent-base mixture is contacted with the metal startingmaterial to form a precipitate of the metal and the porogen. For examplewithout limitation thereto, in the synthesis of TiO₂, NH₄OH may becontacted with the solvent to form the solvent-base solution or mixturewhich is then contacted with titanium chloride or titanium oxychlorideto precipitate the hydrous compound containing titanium and the porogen,ammonium chloride.

The porogen is then removed to form the mesoporous metal oxide productof the invention which can be at least partially agglomerated. Theagglomerated titanium oxide product can be dispersed by methods known tothose skilled in the art to give titanium oxide nanoparticles.

If the porogen is removed by washing with water, a very high surfacearea, high porosity, mesoporous network of amorphous, hydrous metaloxide remains. The amorphous, hydrous metal oxide can be a substantiallyamorphous hydrous metal oxide that contains a minor proportion ofcrystalline titanium oxide.

If the porogen is removed by calcining, a high surface area, highporosity, mesoporous network of metal oxide nanocrystals remains.

In another embodiment of the invention a sufficient quantity of a halidesalt can be added, after precipitating the hydrolyzed metal oxide, tosaturate the liquid medium. A solid recovered from the saturated liquidmedium comprises a hydrolyzed metal compound having pores containing thesaturated liquid medium. The saturated liquid medium is removed from thesolid to recover the mesoporous Group IVB metal oxide.

Typically, the liquid medium is the liquid portion of the mixture ofsolvent, with or without dissolved salt, and hydrous metal oxide. As anexample, without being limited thereto, a titanium starting material iscontacted with water to form a solution. To the solution so formed isadded a base to form a mixture comprising precipitated hydrous metaloxide and liquid medium. To that mixture is added halide salt tosaturate the liquid medium. Thereafter, the mesoporous product isrecovered by removing the saturated liquid,medium. Typically, this isaccomplished by drying to volatilize the liquid and calcining to removethe porogen which remains after drying.

In general, after contacting the starting materials, as described above,they can be mixed, preferably at room temperature, for less than onesecond upto several hours. Normally, mixing for 5-60 minutes willsuffice. The precipitate can be recovered by any convenient methodincluding settling, followed by decanting the supernatant liquid,filtration, centrifugation and so forth.

If a very high surface area hydrous metal oxide is desired, therecovered solid, however collected, can be slurried with fresh water toremove the porogen, optionally, followed by additional washing steps.The hydrous metal oxide recovered by washing the solid to remove theporogen is substantially or completely amorphous, as determined by X-raypowder diffraction, and has a very high surface area, typically at leastabout 400 m²/g, typically in the range of about 400 to about 600 m²/g.The pore volume of the amorphous hydrous metal oxide can be at leastabout 0.4 cc/g, typically in the range of about 0.4 to about 1.0. Thenumber of washing steps required to achieve the desired level of hydrousmetal oxide purity will depend upon the solubility of the porogen, theamount of water employed, and the efficiency of the mixing process. Therecovered solid can be dried by any convenient means including but notlimited to radiative warming and oven heating. As an example, a veryhigh surface area, mesoporous hydrous oxide of titanium having a surfacearea of at least 400 m²/g and pore volume of at least about 0.4 cc/g maybe synthesized using the process of this invention.

If a high surface area, mesoporous, nanocrystalline, metal oxide isdesired, the hydrolyzed metal compound and porogen, however collected,can be calcined at a temperature that removes the porogen. Generally,the calcination temperatures are at least the sublimation ordecomposition temperature of the porogen. Typically the calcinationtemperatures will range from about 300° C. to about 600° C., preferablybetween about 350° C. and about 550° C., and more preferably betweenabout 400° C. and 500° C.

In the case of preparing TiO₂ from TiCl₄ and NH₄OH in saturated aqueousammonium chloride, the 450° C.-calcined product can be composed ofagglomerated nanocrystals of anatase, although some rutile, brookite, orX-ray amorphous material may also be present. The size of the anatasenanocrystals is a function of the calcination temperature andcalcination time. At a calcination temperature of 450° C., the averagecrystallite size can be from about 10-15 nm.

The calcined TiO₂ made by the process of the invention is characterizedby a combination of high surface area, high pore volume, and largeaverage pore diameter. By high surface area is meant at least about 70m²/g, typically, about 70 m²/g up to and including about 100 m²/g, highpore volume of at least about 0.5 cc/g, preferably at least about 0.6cc/g, and large average pore diameter at least about 200 Å, preferablyat least about 300 Å. Generally, the pore volume will range from about0.5 cc/g to about 1.0 cc/g, and the average pore diameter from about 200Å to about 500 Å.

For the titanium oxide, the porogen is present in amounts sufficient toproduce the mesoporous oxide of titanium having the pore volume andaverage pore diameter described in this disclosure. The amount ofporogen sufficient to achieve the results of this disclosure can varydepending upon the porogen, the reaction conditions and the otheringredients (e.g. base, solvent and titanium-containing startingmaterial). However, the concentration of ingredients and reactionconditions can provide for at least 2 moles of porogen to precipitatefor each mole of hydrolyzed compound comprising titanium thatprecipitates. More specifically, for titanium tetrachloride or titaniumoxychloride or mixtures thereof, the concentration of ingredients andreaction conditions can provide for at least 3 moles, even morespecifically 4 moles, of porogen to precipitate for each mole ofhydrolyzed compound comprising titanium that precipitates. While notwishing to be bound by any theory, a high porogen concentration cancontribute to the formation of more pores (which can contribute to ahigh pore volume) and large pores which provide a high average porediameter (which can contribute to a high pore volume).

The crystalline titanium oxide product made by the process of thisinvention can comprise agglomerated nanocrystals predominantly, if notcompletely, having an anatase crystal structure. When the product is notcompletely anatase, a minor amount of rutile, brookite, and/or X-rayamorphous material may be present.

Calcined ZrO₂ made by the process of the invention is also characterizedby a combination of high surface area, high pore volume, and largeaverage pore diameter. For ZrO₂, the high surface is at least about 70m²/g, high pore volume at least about 0.25 cc/g, and large average porediameter of at least about 100 Å, preferably at least about 150 Å.Generally, the pore volume for ZrO₂ thus formed is between about 0.25cc/g and about 0.5 cc/g, and the average pore diameter is between about100 Å and 200 Å.

Calcined HfO₂ made by the process of the invention is also characterizedby a combination of high pore volume and large average pore diameter.For HfO₂, the high surface area is at least about 40 m²/g, high porevolume at least about 0.1 cc/g, and large average pore diameter at leastabout 100 Å, preferably at least about 120 Å. Generally, the pore volumefor HfO₂ is between about 0.1 cc/g and about 0.25 cc/g, and the averagepore diameter is between about 100 Å and about 200 Å.

The process of the invention may be performed in both batch andcontinuous modes. The solvent can be separated and recycled. Thevolatiles can be condensed, then recycled or disposed.

The pH of the system is generally in the range of about 4 to about 10,preferably from about 5 to about 9, and most preferably between about 6and about 8. In a continuous process, the pH of the system is generallycontrolled better than with a batch process because it is believed thatthe material produced is exposed to less environmental variability inpH.

For a continuous mixing process, several process parameters may bevaried in order to achieve high porosity. Such process parametersinclude, but are not limited to, the solvent used for each separateincoming stream, the flow rates, solution/slurry concentrations, anddegree of mixing. In the continuous mixing process of this disclosure,good mixing is important. Good mixing can be achieved by combiningseparate solutions or slurries with fast flow rates through narrowdiameter tubes, to provide turbulent, non laminar mixing which can beachieved using a T-shaped mixer. For example, for tubing having an innerdiameter of about 0.19 inches, the total combined flow rate can begreater than about 500 mL/min., preferably greater than about 1000mL/min., more preferably, greater than about 1500 mL/min. Withoutsufficient mixing, a high-porosity mesoporous material may not form. Theslurry produced using the T-shaped mixer can be collected and furthermixed with any convenient mixing device, such as an overhead stirrer.

In one embodiment of the invention the oxide of titanium, zirconium orhafnium further comprises a dopant which can be a transition metal, aGroup IIA, IIIA, IVA, or VA metal. Specifically, without limitationthereto, the dopant can be Ge, P, As, Sb, Bi, Ni, Cu, Al, Zr, Hf, Si,Nb, Ta, Fe, Sn, Co, Zn, Mo, W, V, Cr, Mn, Mg, Ca, Sr, Ba, Ga, or In.Methods for incorporating dopants into the oxide would be apparent tothose skilled in the art. For example, a dopant-containing compoundcould be added with the titanium, zirconium or hafnium-containingstarting material.

Compositions of matter of this invention can be used as a catalyst orcatalyst support. For example, the catalytic properties of TiO₂ are wellknown to those skilled in the catalyst art. Use of the compositions ofmatter of this invention as catalysts or catalyst supports would beapparent to those skilled in the catalyst art.

Compositions of matter of this invention can be used as nanoparticleprecursors. The Group IVB metal oxide agglomerates formed by the processof this invention can be formed into nanoparticles by any suitabledeagglomeration technique. As an example, product of this invention canbe deagglomerated by mixing the product with water and a suitablesufactant such as, without being limited thereto,tetrasodiumpyrophosphate followed by sonication to break-up theagglomerates. However, other suitable techniques for breaking-up theagglomerates would be apparent to those skilled in the metal oxidepowder art. Typically, deagglomeration is by sonication or mediamilling. The nanoparticle precursor of the invention can bedeagglomerated to a degree sufficient to form agglomerates considered tofall within the nanoparticle size range, typically having an averageagglomerate size diameter which is less than about 200 nanometers.

The deagglomerated titanium dioxide product of this invention, if photopassivated, can be especially useful for UV light degradation resistancein plastics, sunscreens and other protective coatings including paintsand stains.

The titanium dioxide product of this invention can be photo passivatedby treatment with silica and/or alumina by any of several methods whichare well known in the art including, without limit, silica and/oralumina wet treatments used for treating pigment-sized titanium dioxide.

The titanium dioxide product of this invention can also have an organiccoating which may be applied using techniques known by those skilled inthe art. A wide variety of organic coatings are known. Organic coatingsemployed for pigment-sized titanium dioxide may be utilized. Examples oforganic coatings that are well known to those skilled in the art includefatty acids, such as stearic acid; fatty acid esters; fatty alcohols,such as stearyl alcohol; polyols such as trimethylpropane diol ortrimethyl pentane diol; acrylic monomers, oligomers and polymers; andsilicones, such as polydimethylsiloxane and reactive silicones such asmethylhydroxysiloxane.

Organic coating agents can include but are not limited to carboxylicacids such as adipic acid, terephthalic acid, lauric acid, myristicacid, palmitic acid, stearic acid, oleic acid, salicylic acid, malicacid, maleic acid, and esters, fatty acid esters, fatty alcohols, suchas stearyl alcohol, or salts thereof, polyols such as trimethylpropanediol or trimethyl pentane diol; acrylic monomers, oligomers andpolymers. In addition, silicon-containing compounds are also of utility.Examples of silicon compounds include but are not limited to a silicateor organic silane or siloxane including silicate, organoalkoxysilane,aminosilane, epoxysilane, and mercaptosilane such ashexyltrimethoxysilane, octyltriethoxysilane, nonyltriethoxysilane,decyltriethoxysilane, dodecyltriethoxysilane, tridecyltriethoxysilane,tetradecyltriethoxysilane, pentadecyltriethoxysilane,hexadecyltriethoxysilane, heptadecyltriethoxysilane,octadecyltriethoxysilane, N-(2-aminoethyl) 3-aminopropylmethyldimethoxysilane, N-(2-aminoethyl) 3-aminopropyl trimethoxysilane,3-aminopropyl triethoxysilane, 3-glycidoxypropyl trimethoxysilane,3-glycidoxypropyl methyldimethoxysilane, 3-mercaptopropyltrimethoxysilane and mixtures of two or more thereof.Polydimethylsiloxane and reactive silicones such asmethylhydroxysiloxane may also be useful.

The titanium dioxide product of this invention may also be coated with asilane having the formula:R_(x)Si(R′)_(4-x)wherein

-   -   R is a nonhydrolyzable aliphatic, cycloaliphatic or aromatic        group having at least 1 to about 20 carbon atoms;    -   R′ is a hydrolyzable group such as an alkoxy, halogen, acetoxy        or hydroxy or mixtures thereof; and    -   x=1 to 3.        For example, silanes useful in carrying out the invention        include hexyltrimethoxysilane, octyltriethoxysilane,        nonyltriethoxysilane, decyltriethoxysilane,        dodecyltriethoxysilane, tridecyltriethoxysilane,        tetradecyltriethoxysilane, pentadecyltriethoxysilane,        hexadecyltriethoxysilane, heptadecyltriethoxysilane and        octadecyltriethoxysilane. Additional examples of silanes        include, R=8-18 carbon atoms; R′=chloro, methoxy, hydroxy or        mixtures thereof; and x=1 to 3. Preferred silanes are R=8-18        carbon atoms; R′=ethoxy; and x=1 to 3. Mixtures of silanes are        contemplated equivalents. The weight content of the treating        agent, based on total treated particles can range from about 0.1        to about 10 wt. %, additionally about 0.7 to about 7.0 wt. % and        additionally from about 0.5 to about 5 wt %.

The titanium dioxide particles of this invention can be silanized asdescribed in U.S. Pat. Nos. 5,889,090; 5,607,994; 5,631,310; and5,959,004 which are each incorporated by reference herein in theirentireties.

The titanium dioxide product of this invention may be treated to haveany one or more of the foregoing organic coatings.

Titanium dioxide product made according to the present invention may beused with advantage in various applications including withoutlimitation, coating formulations such as sunscreens, cosmetics,automotive coatings, wood coatings, and other surface coatings; chemicalmechanical planarization products; catalyst products; photovoltaiccells; plastic parts, films, and resin systems including agriculturalfilms, food packaging films, molded automotive plastic parts, andengineering polymer resins; rubber based products including siliconerubbers; textile fibers, woven and nonwoven applications includingpolyamide, polyaramid, and polyimides fibers products and nonwovensheets products; ceramics; glass products including architectural glass,automotive safety glass, and industrial glass; electronic components;and other uses in which photo and chemically passivated titanium dioxidewill be useful.

Thus in one embodiment, the invention is directed to a coatingcomposition suitable for protection against ultraviolet light comprisingan additive amount suitable for imparting protection against ultravioletlight of photo passivated titanium dioxide nanoparticles made inaccordance with this invention dispersed in a protective coatingformulation.

One area of increasing demand for titanium dioxide nanoparticles is incosmetic formulations, particularly in sunscreens as a sunscreen agent.Titanium dioxide nanoparticles provide protection from the harmfulultraviolet rays of the sun (UV A and UV B radiation).

A dispersant is usually required to effectively disperse titaniumdioxide nanoparticles in a fluid medium. Careful selection ofdispersants is important. Typical dispersants for use with titaniumdioxide nanoparticles include aliphatic alcohols, saturated fatty acidsand fatty acid amines.

The titanium dioxide nanoparticles of this invention can be incorporatedinto a sunscreen formulation. Typically the amount of titanium dioxidenanoparticles can be up to and including about 25 wt. %, typically fromabout 0.1 wt. % up to and including about 15 wt. %, even more preferablyup to and including about 6 wt. %, based on the weight of theformulation, the amount depending upon the desired sun protection factor(SPF) of the formulation. The sunscreen formulations are usually anemulsion and the oil phase of the emulsion typically contains the UVactive ingredients such as the titanium dioxide particles of thisinvention. Sunscreen formulations typically contain in addition towater, emollients, humectants, thickeners, UV actives, chelating agents,emulsifiers, suspending agents (typically if using particulate UVactives), waterproofers, film forming agents and preservatives.

Specific examples of preservatives include parabens. Specific examplesof emollients include octyl palmitate, cetearyl alcohol, anddimethicone. Specific examples of humectants include propylene glycol,glycerin, and butylene glycol. Specific examples of thickeners includexanthan gum, magnesium aluminum silicate, cellulose gum, andhydrogenated castor oil. Specific examples of chelating agents includedisodium ethylene diaminetetraacetic acid (EDTA) and tetrasodium EDTA.Specific examples of UV actives include ethylhexyl methoxycinnamate,octocrylene, and titanium dioxide. Specific examples of emulsifiersinclude glyceryl stearate, polyethyleneglycol-100 stearate, andceteareth-20. Specific examples of suspending agents includediethanolamine-oleth-3-phosphate and neopentyl glycol dioctanoate.Specific examples of waterproofers include C30-38 olefin/isopropylmaleate/MA copolymer. Specific examples of film forming agents includehydroxyethyl cellulose and sodium carbomer.

To facilitate use by the customer, producers of titanium dioxidenanoparticles may prepare and provide dispersions of the particles in afluid medium which are easier to incorporate into formulations.

Water based wood coatings, especially colored transparent and clearcoatings benefit from a UV stabilizer which protects the wood. OrganicUV absorbers are typically hydroxybenzophenones and hydroxyphenylbenzotriazoles. A commercially available UV absorber is sold under thetrade name Tinuvin™ by Ciba. These organic materials, however, have ashort life and decompose on exterior exposure. Replacing some or all ofthe organic material with titanium dioxide nanoparticles would allowvery long lasting UV protection. Photo passivated titanium dioxide ofthis invention may be used to prevent the titanium dioxide fromoxidizing the polymer in the wood coating, and be sufficientlytransparent so the desired wood color can be seen. Because most woodcoatings are water based, the titanium dioxide needs to be dispersiblein the water phase. Various organic surfactants known in the art can beused to disperse the titanium dioxide nanoparticles in water.

Many cars are now coated with a clear layer of polymer coating toprotect the underlying color coat, and ultimately the metal body parts.This layer has organic UV protectors, and like wood coatings, a morepermanent replacement for these materials is desired. The clear coatlayers are normally solvent based, but can also be water based. Suchcoatings are well known in the art. The titanium dioxide nanoparticlesof this invention can be modified for either solvent or water basedsystems with appropriate surfactants or organic surface treatments.

When treated for reduced photo activity, the titanium dioxide particlesof this invention can be beneficial in products which degrade uponexposure to UV light energy such as thermoplastics and surface coatings.

Titanium dioxide nanoparticles can also be used to increase themechanical strength of thermoplastic composites. Most of theseapplications also require a high degree of transparency and passivationso underlying color or patterns are visible and the plastic is notdegraded by the photoactivity of the titanium dioxide nanoparticles. Thetitanium dioxide nanoparticles must be compatible with the plastic andeasily compounded into it. This application typically employs organicsurface modification of the titanium dioxide nanoparticles as describedherein above. The foregoing thermoplastic composites are well known inthe art.

Polymers which are suitable as thermoplastic materials for use in thepresent invention include, by way of example but not limited thereto,polymers of ethylenically unsaturated monomers including olefins such aspolyethylene, polypropylene, polybutylene, and copolymers of ethylenewith higher olefins such as alpha olefins containing 4 to 10 carbonatoms or vinyl acetate, etc.; vinyls such as polyvinyl chloride,polyvinyl esters such as polyvinyl acetate, polystyrene, acrylichomopolymers and copolymers; phenolics; alkyds; amino resins; epoxyresins, polyamides, polyurethanes; phenoxy resins, polysulfones;polycarbonates; polyether and chlorinated polyesters; polyethers; acetalresins; polyimides; and polyoxyethylenes. The polymers according to thepresent invention also include various rubbers and/or elastomers eithernatural or synthetic polymers based on copolymerization, grafting, orphysical blending of various diene monomers with the above-mentionedpolymers, all as generally well known in the art. Thus generally, thepresent invention is useful for any plastic or elastomeric compositions( which can also be pigmented with pigmentary TiO₂). For example, butnot by way of limitation, the invention is felt to be particularlyuseful for polyolefins such as polyethylene and polypropylene, polyvinylchloride, polyamides and polyester.

From the refractive index of compositions of matter of this invention itwould be apparent to those skilled in the optics art that thecompositions of this invention can be useful in optics. The TiO₂ productof this invention could be mixed with polymethylmethacrylate polymer andmade into an optical device. Other techniques for incorporating thecompositions of this invention into optical devices would be apparent tothose skilled in the art of making optical devices.

Additionally, compositions of matter of this invention can be useful inelectronics. For example the TiO₂ product of this invention could beused in photovoltaic devices. As an example, a TiO₂ product can be mixedwith a binder and cast into a film on a conducting substrate bywell-known techniques to form a component of an anode which can be usedin a solar cell. Other suitable techniques for incorporating products ofthis invention into photovoltaic devices would be apparent to thoseskilled in the electronics art. TiO₂ products of this invention canprovide high powder conversion efficiency in solar cell applications.

Compositions of matter of this invention can be used in a battery as amajor component of the anode. For example, the electrochemicalproperties of titanium in a lithium battery are well known to thoseskilled in the battery art and the titanium dioxide product of thisinvention can be used in making an anode of a battery by techniquesknown to those skilled in the battery art.

In one embodiment, the invention herein can be construed as excludingany element or process step that does not materially affect the basicand novel characteristics of the composition or process. Additionally,the invention can be construed as excluding any element or process stepnot specified herein.

Further, when an amount, concentration, or other value or parameter isgiven as either a range, preferred range, or a list of upper preferablevalues and lower preferable values, this is to be understood asspecifically disclosing all ranges formed from any pair of any upperrange limit or preferred value and any lower range limit or preferredvalue, regardless of whether ranges are separately disclosed. Where arange of numerical values is recited herein, unless otherwise stated,the range is intended to include the endpoints thereof, and all integersand fractions within the range. It is not intended that the scope of theinvention be limited to the specific values recited when defining arange.

The examples which follow, description of illustrative and preferredembodiments of the present invention are not intended to limit the scopeof the invention. Various modifications, alternative constructions andequivalents may be employed without departing from the true spirit andscope of the appended claims.

cl Test Methods

The following test methods and procedures were used in the Examplesbelow:

Nitrogen Porosimetry: Dinitrogen adsorption/desorption measurements wereperformed at 77.3 K on Micromeritics ASAP model 2400/2405 porosimeters(Micromeritics Inc., One Micromeritics Drive, Norcross Ga. 30093-1877).Samples were degassed at 150° C. overnight prior to data collection.Surface area measurements utilized a five-point adsorption isothermcollected over 0.05 to 0.20 p/p₀ and analyzed via the BET method(described in S. Brunauer, P. H. Emmett and E. Teller, J. Amer. Chem.Soc., 60, 309 (1938)). Pore volume distributions utilized a 27 pointdesorption isotherm and were analyzed via the BJH method (described inE. P. Barret, L. G. Joyner and P. P. Halenda, J. Amer. Chem. Soc., 73,373 (1951)). Values for pore volume represent the single point totalpore volume of pores less than about 3000 angstroms. Average porediameter, D, is determined by D=4V/A, where V is the single point totalpore volume and A is the BET surface area.

X-ray Powder Diffraction: Room-temperature powder x-ray diffraction datawere obtained with a Philips X'PERT automated powder diffractometer,Model 3040. Samples were run in batch mode with a Model PW 1775 or ModelPW 3065 multi-position sample changer. The diffractometer was equippedwith an automatic variable slit, a xenon proportional counter, and agraphite monochromator. The radiation was CuK(alpha) (45 kV, 40 mA).Data were collected from 2 to 60 degrees 2-theta; a continuous scan withan equivalent step size of 0.03 deg; and a count time of 0.5 seconds perstep.

Thermogravimetric Analysis: About 5-20 mg samples were loaded intoplatinum TGA pans. Samples were heated in a TA Instruments 2950 TGAunder 60 ml/min air purge and 40 ml/min N₂ in the balance area (totalpurge rate was 100 ml/min). Samples were heated from RT to 800° C. at10° C./min. The temperature scale of the TGA was previously calibratedat the 10° C./min rate using thermomagnetic standards.

Ionic Conductivity: Ionic conductivity was measured with a VWR traceableconductivity/resistivity/salinity concentration meter. The ionicconductivity of the wash sollutions was used to determine when themajority of the NH₄Cl salt had been removed.

Particle Size Distribution (PSD): Particle size distribution wasmeasured with a Malvern Nanosizer Dynamic Light Scattering Unit onsuspensions containing 0.1 wt % TiO₂.

Index of Refraction: The index of refraction of samples was measuredwith a Metricon Prism Coupler, Model 2010, with four wavelengthsavailable (633, 980, 1310 and 1550 nm). This instrument interprets theamount of light coupled into a sample that is pressed into contact witha high index prism. The light enters the sample from the prism side andthe angle of incidence is varied. The wavelength selected in theexamples below was 1550 nm. The sample was placed against the prism andheld in close optical contact with the prism by a pneumatic ram. Thesample surface was flat, smooth and clean, and of uniform thickness. Thealigned laser light hit the optically contacted spot between the sampleand the prism, and the index of refraction was obtained from a plot ofintensity versus angle of incidence.

Photo Voltaic Power Efficiency: Photo voltaic power efficiency (“PVPE”)was measured using photoelectrochemical techniques as described insection 2.5 of M. K. Nazeeruddin, et al., J. Am. Chem. Soc., Vol. 123,pp.1613-1624, 2001. Data were obtained by using a 450 W xenon lightsource that was focused to give 1000 W/m², at the surface of the testcell, and measuring the output with a digital source meter. Theinformation was analyzed after data acquisition.

EXAMPLES

In the following Examples and Comparative Examples, reaction products ofa Group IVB metals were formed and characterized. Surface area andporosity data are summarized in Table 6 and were obtained by theprocedures described above.

All chemicals and reagents were used as received from: TiCl₄ AldrichChemical Co., Milwaukee, WI, 99.9% ZrOCl₂.8H₂O Alfa Aesar, Ward Hill,MA, 99.9% HfOCl₂.8H₂O Alfa Aesar, Ward Hill, MA, 99.98% ethanol Pharmco,Brookfield, CT, ACS/USP Grade 200 Proof NH₄OH EMD Chemicals, Gibbstown,NJ, 28.0-30.0% NH₄Cl EMD Chemicals, Gibbstown, NJ, 99.5% n-propanol EMDChemicals, Gibbstown, NJ, 99.99% isopropanol EMD Chemicals, Gibbstown,NJ, 99.5% n-butanol EMD Chemicals, Gibbstown, NJ, 99.97% iso-butanol EMDChemicals, Gibbstown, NJ, 99.0% tert-butanol EMD Chemicals, Gibbstown,NJ, 99.0% DMAc EMD Chemicals, Gibbstown, NJ, 99.9% (N, N′dimethylacetamide) acetone EMD Chemicals, Gibbstown, NJ, 99.5% (reagentbottle) TiO₂ Degussa Inc., Parsipanny, NJ, P25 TSPPtetrasodiumpyrophosphate (CAS number 7722-88-5)

All references herein to elements of the Periodic Table of the Elementsare to the CAS version of the Periodic Table of the Elements.

In Comparative Examples A, B, C, D, and in Examples 1-5, 7-9 and 11, theamount of 50 wt. % TiCl₄ in water is the source of titanium oxychloride.

Comparative Example A

This example illustrates that reaction of titanium oxychloride and NH₄OHin water alone does not produce a TiO₂ product, uncalcined or calcined,having the surface area and porosity properties of TiO₂ made byprocesses of this invention. The precipitate formed from the reaction oftitanium oxychloride and NH₄OH in water is washed extensively to removeany trapped NH₄Cl byproduct.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mLdeionized water while stirring with a Teflon coated magnetic stirringbar in a 400 mL Pyrex beaker. With stirring, 14.5 mL concentrated NH₄OH(i.e., ˜30% wt =14.8 M) were added to the titanium solution. The pH ofthe slurry, measured with multi-color strip pH paper, was about 7. Theresulting slurry was stirred for 60 minutes at ambient temperature.

The solid was washed extensively with deionized water until the clear,colorless supernatant wash water had a low ionic conductivity value, 12μS/cm. The solid was collected by suction filtration and dried under anIR heat lamp. An X-ray powder diffraction pattern showed the material tobe amorphous. Nitrogen porosimetry measurements of this uncalcinedpowder revealed a surface area of 398 m²/g, a pore volume of 0.37 cc/g,and an average pore diameter of 37 Å.

The powder was transferred to an alumina crucible and heated uncoveredfrom room temperature to 450° C. over the period of one hour, and heldat 450° C. for an additional hour. The crucible and its contents wereremoved from the furnace and cooled naturally to room temperature.

An X-ray powder diffraction pattern of the calcined material showed onlythe broad lines of anatase indicating an average crystal size of 16 nm.Nitrogen porosimetry revealed a surface area of 72 m²/g, a pore volumeof 0.17 cc/g, and an average pore diameter of 95 Å. FIG. 1 is a scanningelectron microscope (SEM) image of the calcined powder, at amagnification of 50,000×, showing the product is compacted with lowporosity. The porosimetry data of this Example are reported in Table 6.

Comparative Example B

This example also illustrates that reaction of titanium oxychloride andNH₄OH in water alone does not produce a TiO₂ product, uncalcined orcalcined, having the surface area and porosity properties of a TiO₂product of this invention. Here, the precipitate formed from thereaction of titanium oxychloride and NH₄OH in water is collected andprocessed without the washing step used in Comparative Example A toremove NH₄Cl byproduct.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mLdeionized water while stirring with a Teflon coated magnetic stirringbar in a 400 mL Pyrex beaker. With stirring, 28 mL 1:1 NH₄OH (i.e.,14-15% wt=7.5 M) were added to the titanium solution. The pH of theslurry, measured with multi-color strip pH paper, was about 5. Theresulting slurry was stirred for 60 minutes at ambient temperature.

The unwashed solid was collected by suction filtration and dried underan IR heat lamp. An X-ray powder diffraction pattern showed the lines ofNH₄Cl and a trace of anatase. Nitrogen porosimetry measurements of thismixture revealed a surface area of 215 m²/g, a pore volume of 0.17 cc/g,and an average pore diameter of 31 Å.

The powder was transferred to an alumina crucible and heated uncoveredfrom room temperature to 450° C. over the period of one hour, and heldat 450° C. for an additional hour. The crucible and its contents wereremoved from the furnace and cooled naturally to room temperature.

An X-ray powder diffraction pattern of the calcined material showedbroad lines of anatase as the most intense and also showed one line ofbrookite with very low intensity. Nitrogen porosimetry revealed asurface area of 70 m²/g, a pore volume of 0.25 cc/g, and an average porediameter of 146 Å. The porosimetry data of this Example are reported inTable 6.

Comparative Example C

This example illustrates that reaction of titanium oxychloride and NH₄OHusing acetone as the solvent does not result in a calcined TiO₂ havingthe surface area and porosity properties of a calcined TiO₂ product madeby the process of this invention.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mLacetone while stirring with a Teflon coated magnetic stirring bar in a400 mL Pyrex beaker. With stirring, 28 mL 1:1 NH₄OH (i.e., 14-15% wt=7.5M) were added to the titanium solution. The pH of the slurry, measuredwith water moistened multi-color strip pH paper, was about 7. Theresulting slurry was stirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp to yield 14.5 g of white powder. An X-ray powder diffractionpattern showed only the lines of NH₄Cl.

The powder was transferred to an alumina crucible and heated uncoveredfrom room temperature to 450° C. over the period of one hour, and heldat 4500C for an additional hour. The crucible and its contents wereremoved from the furnace and cooled naturally to room temperature. Itwas observed that the volume of powder after calcination was about halfthe volume of the starting precalcined powder.

An X-ray powder diffraction pattern of the calcined material showedbroad lines of anatase as the most intense, and also showed some linesof rutile with very low intensity, as well as some amorphous material.Nitrogen porosimetry revealed a surface area of 75.8 m²/g, a pore volumeof 0.24 cc/g, and an average pore diameter of 129 Å. The porosimetrydata of this Example are reported in Table 6.

Comparative Example D

This example describes that reaction of titanium oxychloride and NH₄OHin the three butanol isomers to form TiO₂.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mLn-butanol, tert-butyl alcohol, and isobutyl alcohol, respectively, whilestirring with a Teflon coated magnetic stirring bar in 400 mL Pyrexbeakers. With stirring, 29 mL 1:1 NH₄OH (i.e., 14-15% wt=7.5 M) wereadded to each of the three titanium solutions. The pH of the slurrieswas measured with water moistened multi-color strip pH paper andobserved to be in the range of ˜6-7. The slurries were stirred for 60minutes at ambient temperature.

The solids were each collected by suction filtration and dried under anIR heat lamp to give yields of 14.7 g, 13.3 g, and 13.1 g, respectively.X-ray powder diffraction patterns showed only the lines of NH₄Cl for then-butanol and tert-butyl alcohol reactions, and a trace of anatase inaddition to NH₄Cl for the isobutyl alcohol reaction.

The powders were transferred to alumina crucibles and heated, uncovered,from room temperature to 450° C. over the period of one hour, and heldat 450° C. for an additional hour. The crucibles and their contents wereremoved from the furnace and cooled naturally to room temperature. X-raypowder diffraction patterns of the calcined materials showed thecrystalline phases reported in Table 1: TABLE 1 Butanol Crystallinephases determined by solvent XPD n-butanol anatase, trace of brookitetert-butyl alcohol anatase isobutyl alcohol anatase, NH₄Cl, small amountof rutile

Nitrogen porosimetry revealed the following surface areas, pore volumes,and average pore diameters reported in Table 2: TABLE 2 surface areaave. pore diam. (m²/g) pore vol. (cc/g) (Å) (I) n-butanol 82 0.4 193(II) tert-butyl 74 0.37 202 alcohol (III) isobutyl 109 0.28 105 alcohol

As shown in Table 2, the TiO₂ product formed in accordance with theprocedure of this Comparative Example D, wherein the solvent was each ofthe three different butanol isomers, did not have the porosityproperties of TiO₂ produced by the process of this invention. Theporosimetry data of this Example are also reported in Table 6.

Example 1

This example illustrates that reaction of titanium oxychloride and NH₄OHin aqueous saturated NH₄Cl can produce a calcined mesoporousnanocrystalline TiO₂ powder having a high surface area and highporosity. 20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about250 mL aqueous NH₄Cl solution, made by dissolving 73 g NH₄Cl in 200 gdeionized H₂O, with stirring with a Teflon coated magnetic stirring barin a 400 mL Pyrex beaker. With continued stirring, 30 mL 1:1 NH₄OH(i.e., 14-15% wt or 7.5 M) were added to the titanium-chloride/ammoniumchloride solution. The pH of the slurry, measured with multi-color strippH paper, was about 7. The resulting slurry was stirred for 60 minutesat ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp to yield 14.9 g of white powder. The powder was then transferred toan alumina crucible and heated uncovered from room temperature to 4500Cover the period of one hour, and held at 450° C. for an additional hourto ensure removal of the volatile NH₄Cl. The crucible and its contentswere removed from the furnace and cooled naturally to room temperature.

An X-ray powder diffraction pattern of the calcined material showed onlybroad lines of anatase and from the width of the strongest peak anaverage crystal size of 12 nm was estimated (see FIG. 2). Nitrogenporosimetry revealed a surface area of 88 m²/g, a pore volume of 0.72cc/g, and an average pore diameter of 325 Å. The porosimetry data ofthis Example are reported in Table 6.

Example 2

This example illustrates that reaction of titanium oxychloride and NH₄OHin absolute ethanol can produce a calcined mesoporous nanocrystallineTiO₂ powder having a high surface area and high porosity.

15 mL concentrated NH₄OH were added to about 200 mL absolute ethanolwhile stirring with a Teflon coated magnetic stirring bar in a 400 mLPyrex beaker. With stirring, 20.0 g (14 mL) of 50 wt. % TiCl₄ in waterwere added to the basic solution. The pH of the slurry, measured withwater moistened multi-color strip pH paper, was about 8. The resultingslurry was stirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina boat and heated uncoveredfrom room temperature to 450° C. over the period of one hour, and heldat 450° C. for an additional hour. The furnace with the boat and itscontents were cooled naturally to room temperature. An X-ray powderdiffraction pattern of the calcined material showed only the broad linesof anatase. Nitrogen porosimetry revealed a surface area of 84 m²/g, apore volume of 0.78 cc/g, and an average pore diameter of 371 Å. Theporosimetry data of this Example are reported in Table 6.

Example 3

This example illustrates that adding NH₄OH to a solution of titaniumoxychloride in n-propanol can produce a calcined mesoporousnanocrystalline TiO₂ powder having a high surface area and highporosity. 20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about200 mL n-propanol while stirring with a Teflon coated magnetic stirringbar in a 400 mL Pyrex beaker. With stirring, 28 mL 1:1 NH₄OH (i.e.,14-15% wt or 7.5 M) were added to the titanium solution. The pH of theslurry, measured with water moistened multi-color strip pH paper, wasabout 6. The resulting slurry was stirred for 60 minutes at ambienttemperature.

The solid was collected by suction filtration and dried under an IR heatlamp to yield 13.0 g of white powder. An X-ray powder diffractionpattern showed only the lines of NH₄Cl. The powder was transferred to analumina crucible and heated uncovered from room temperature to 450° C.over the period of one hour, and held at 450° C. for an additional hourto ensure removal of the volatile NH₄Cl. The crucible and its contentswere removed from the furnace and cooled naturally to room temperature.Surprisingly, the volume of powder after calcination was almost the sameas that of the starting pre-calcined powder, even though the amount ofNH₄Cl in the starting mixture was ˜65% by weight.

Nitrogen porosimetry revealed a surface area of 89 m²/g, a pore volumeof 0.65 cc/g, and an average pore diameter of 293 Å. A Scanning ElectronMicroscopy image at 30,000× magnification, FIG. 3, shows porousagglomerates of TiO₂ crystals. The porosimetry data of this Example arereported in Table 6.

Example 4

This example illustrates that adding titanium oxychloride to a solutionof NH₄OH in n-propanol can produce a calcined mesoporous nanocrystallineTiO₂ powder having a high surface area and high porosity.

37.5 mL concentrated NH₄OH were added to about 500 mL n-propanol whilestirring with a Teflon coated magnetic stirring bar in a 1 L Pyrexbeaker. With continued stirring, 35 mL of 50 wt. % TiCl₄ in water wereadded to the NH₄OH-propanol solution. The resulting slurry with pH 7 wasstirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The voluminous powder was transferred to alumina boats and heateduncovered, under flowing air in a tube furnace, from room temperature toabout 450° C. over the period of one hour, and held at about 450° C. foran additional hour to ensure removal of the volatile NH₄Cl. The furnacewas allowed to cool naturally to room temperature, and the firedmaterial was recovered.

An X-ray powder diffraction pattern of the calcined material showed thebroad lines of anatase and a trace of rutile. Nitrogen porosimetryrevealed a surface area of 86 m²/g, a pore volume of 0.93 cc/g, and anaverage pore diameter of 435 Å. FIG. 4 is a Scanning Electron Microscopyimage of the product of this Example at 50,000× magnification showingvery porous agglomerates of TiO₂ crystals. The porosimetry data of thisExample are reported in Table 6.

Example 5

This example, where NH₄OH is added to a solution of titanium oxychloridein n-propanol in the presence of a surfactant, describes a calcinedmesoporous nanocrystalline TiO₂ powder having a high surface area andhigh porosity.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mL of5% wt Pluronic P123 (BASF Corp) surfactant in n-propanol while stirringwith a Teflon coated magnetic stirring bar in a 400 mL Pyrex beaker.With stirring, 29 mL 1:1 NH₄OH (i.e., 14-15% wt or 7.5 M) were added tothe titanium solution. The resulting slurry was stirred for 60 minutesat ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp to yield 14.1 g of white powder. The powder was transferred to analumina crucible and heated uncovered from room temperature to 450° C.over the period of one hour, and held at 450° C. for an additional hourto ensure removal of the volatile NH₄Cl template. The crucible and itscontents were removed from the furnace and cooled naturally to roomtemperature. An X-ray powder diffraction pattern of the calcinedmaterial showed broad lines of anatase (14 nm average crystal size), anda very small amount of rutile. Nitrogen porosimetry revealed a surfacearea of 91 m²/g, a pore volume of 0.63 cc/g, and an average porediameter of 276 Å. FIGS. 5 and 6 are scanning electron microscopy imageswith magnifications of 25,000× and 50,000×, respectively, showing veryporous agglomerates of TiO₂ particles. The porosimetry data of thisExample are reported in Table 6.

Example 6

This example illustrates that starting with neat TiCl₄ and concentratedaqueous NH₄OH in n-propanol results in a calcined mesoporousnanocrystalline TiO₂ powder having a high surface area and highporosity.

10 g of 99.995 TiCl₄ were added to about 200 mL n-propanol whilestirring with a Teflon coated magnetic stirring bar in a 400 mL Pyrexbeaker. With stirring, 16 mL concentrated NH₄OH were added to thetitanium solution. The thick slurry was thinned with an additional smallportion of n-propanol. The pH of the slurry, measured with watermoistened multi-color strip pH paper, was about 7-8. The resultingslurry was stirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp to yield 16.1 g of white powder. An X-ray powder diffractionpattern showed only the lines of NH₄Cl. A TGA of this mixture exhibiteda total weight loss of 74% up to ˜300° C. indicating that most of theNH₄Cl had been precipitated along with the TiO₂.

The powder was transferred to an alumina crucible and heated uncoveredfrom room temperature to 450° C. over the period of one hour, and heldat 450° C. for an additional hour to ensure removal of the volatileNH₄Cl. The crucible and its contents were removed from the furnace andcooled naturally to room temperature. An X-ray powder diffractionpattern of the calcined material showed broad lines of anatase, a verysmall amount of brookite, and some amorphous material. Nitrogenporosimetry revealed a surface area of 89 m²/g, a pore volume of 0.56cc/g, and an average pore diameter of 251 Å. The porosimetry data ofthis Example are reported in Table 6.

Example 7

This example illustrates that adding NH₄OH to a solution of titaniumoxychloride in isopropanol results in a calcined mesoporousnanocrystalline TiO₂ powder having a high surface area and highporosity.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mLisopropanol while stirring with a Teflon coated magnetic stirring bar ina 400 mL Pyrex beaker. With stirring, 30 mL 1:1 NH₄OH (i.e., 14-15% wtor 7.5 M) were added to the titanium solution. The resulting slurry wasstirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. An X-ray powder diffraction pattern showed only the lines ofNH₄Cl.

The powder was transferred to an alumina crucible and heated uncoveredfrom room temperature to 450° C. over the period of one hour, and heldat 450° C. for an additional hour to ensure removal of the volatileNH₄Cl. The crucible and its contents were removed from the furnace andcooled naturally to room temperature.

An X-ray powder diffraction pattern of the calcined material showed onlybroad lines of anatase and some amorphous material. The averagecrystallite size of the anatase was estimated to be 11 nm from X-raypeak broadening analysis. Nitrogen porosimetry revealed a surface areaof 78 m²/g, a pore volume of 0.74 cc/g, and an average pore diameter of378 Å. The porosimetry data of this Example are reported in Table 6.

Example 8

This example illustrates that adding NH₄OH to a solution of titaniumoxychloride in N,N′ dimethylacetamide (DMAC) resulted in a calcinedmesoporous nanocrystalline TiO₂ powder having a high surface area andhigh porosity.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mLN,N′ dimethylacetamide (DMAC) while stirring with a Teflon coatedmagnetic stirring bar in a 400 mL Pyrex beaker. With stirring, 29 mL 1:1NH₄OH were added to the titanium solution. The resulting slurry wasstirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina crucible and heateduncovered from room temperature to 450° C. over the period of one hour,and held at 450° C. for an additional hour to ensure removal of thevolatile NH₄Cl porogen. The crucible and its contents were removed fromthe furnace and cooled naturally to room temperature. An X-ray powderdiffraction pattern of the calcined material showed only broad lines ofanatase with an average crystallite size of 13 nm. Nitrogen porosimetryrevealed a surface area of 88 m²/g, a pore volume of 0.68 cc/g, and anaverage pore diameter of 313 Å. The porosimetry data of this Example arereported in Table 6.

Example 9

This example illustrates that addition of NH₄Cl to the aqueous slurryformed by reaction of NH₄OH with titanium oxychloride results in acalcined mesoporous nanocrystalline TiO₂ powder having a high surfacearea and high porosity.

20.0 g (14 mL) of 50 wt. % TiCl₄ in water were added to about 200 mLdeionized H₂O while stirring with a Teflon coated magnetic stirring barin a 400 mL Pyrex beaker. With stirring, 29 mL 1:1 NH₄OH (i.e., 14-15%wt or 7.5 M) were added to the titanium solution. The pH of the slurrywas about 8. After a few minutes, 89 g NH₄Cl were added to the slurry,and the mixture was stirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. An X-ray powder diffraction pattern showed only the lines ofNH₄Cl. The powder was transferred to an alumina crucible and heateduncovered from room temperature to about 450° C. over the period of onehour, and held at about 450° C. for an additional hour to ensure removalof the volatile NH₄Cl. The crucible and its contents were removed fromthe furnace and cooled naturally to room temperature.

An X-ray powder diffraction pattern of the calcined material showed thebroad lines of anatase and a very small amount of brookite. Nitrogenporosimetry revealed a surface area of 80 m²/g, a pore volume of 0.52cc/g, and an average pore diameter of 260 Å. The porosimetry data ofthis Example are reported in Table 6.

Example 10

This example illustrates that adding NH₄OH to a solution of TiCl₄ inn-propanol resulted in a washed and dried, uncalcined, mesoporous, TiO₂powder having a very high surface area and high porosity.

12.5 g TiCl₄ were added to about 200 mL n-propanol while stirring with aTeflon coated magnetic stirring bar in a 400 mL Pyrex beaker. Withstirring, 19 mL concentrated NH₄OH were added to the titanium solution.The resulting slurry was stirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The mixture was slurried in 1 L deionized water, stirred for 15minutes, and collected by suction filtration. The latter step wasrepeated, but this time stirring of the slurry was extended to 90minutes. After overnight drying at room temperature, a voluminous 7.7 gof powder was recovered. An X-ray powder diffraction pattern showed thewashed TiO₂ to be amorphous. Nitrogen porosimetry measurements on thismixture revealed a surface area of 511 m²/g, a pore volume of 0.86 cc/g,and an average pore diameter of 68 Å. The porosimetry data of thisExample are reported in Table 6.

Comparative Example E

This example shows that calcination of the washed and dried TiO₂ productof Example 10, which no longer contains sufficient NH₄Cl porogen, doesnot give a nanocrystalline TiO₂ powder having the high surface area andhigh porosity of TiO₂ made by processes of this invention.

The washed and dried powder in Example 10 was transferred to an aluminacrucible and heated uncovered from room temperature to 450° C. over theperiod of one hour, and held at 450° C. for an additional hour to ensureremoval of the volatile NH₄Cl. The crucible and its contents wereremoved from the furnace and cooled naturally to room temperature. X-raypowder diffraction of the calcined material showed only broad lines ofanatase and some amorphous material. Nitrogen porosimetry revealed asurface area of 61 m²/g, a pore volume of 0.34 cc/g, and an average porediameter of 223 <. The porosimetry data of this Example are reported inTable 6.

Example 11

This example, where NH₄OH is added to a solution of titanium oxychloridein n-propanol in the presence of a surfactant, describes a washed anddried, uncalcined mesoporous TiO₂ powder having a very high surface areaand high porosity.

Example 5 was repeated, but rather than drying and calcining, thefiltered, undried product cake was slurried with 1 L deionized water,stirred for 75 minutes, and collected by suction filtration. Thiswashing step was repeated two more times. The filtered white powder wasdried under an IR heat lamp. An X-ray powder diffraction pattern showedthe washed and dried product to be amorphous. Nitrogen porosimetryrevealed a surface area of 526 m²/g, a pore volume of 0.47 cc/g, and anaverage pore diameter of 35 Å. The porosimetry data of this Example arereported in Table 6.

Example 12

This example demonstrates the utility of the mesoporous, titaniumdioxide product as a nanoparticle precursor. Micron size TiO₂ particlesare deagglomerated by a factor of 100-500, e.g., particles having a d₅₀˜50 μm are reduced in size to have d₅₀ ˜0.100 μm (100 nm).

TiO₂ powders from Examples 1, 4, and 5 above were dispersed by shakingin water containing 0.1 wt % TSPP surfactant. The particle sizedistributions for these powders before and after 20 minutes ofsonication are shown in Table 3. TABLE 3 d₅₀ (μm) after 20 min. TiO₂powder d₅₀ (μm) as prepared sonication Example 1 46.7 0.088 Example 411.3 0.110 Example 5 23.7 0.130

Example 13

This example demonstrates the utility of the nanocrystalline, mesoporoustitanium dioxide in a photovoltaic device. TiO₂ powder made as describedin Example 3, was blended with a binder and cast into a film on anelectrically-conducting fluorine-doped tin-oxide (FTO) coated glasssubstrate. This anode was assembled into a dye-sensitized solar cell andtested as described in section 2.5 of “Engineering of EfficientPanchromatic Sensitizers for Nanocrystalline TiO₂-Based Solar Cells”, M.K. Nazeeruddin, et al., J. Am. Chem. Soc., volume 123, pp. 1613-1624,2001. A control experiment using Degussa P25 TiO₂ was used forcomparison. The cell containing TiO₂ of this invention exhibited ahigher power conversion efficiency, relative to that of the controlcell. The results are reported in Table 4. TABLE 4 Relative powerconversion TiO₂ film efficiency Example 3 1.13 Degussa 1.00 P25

Example 14

This example demonstrates the utility of the nanocrystalline, mesoporoustitanium dioxide in an optical device. The index of refraction of apolymethylmethacrylate (PMMA) polymer film was modified by blending thePMMA polymer with TiO₂ powder from Example 4 to make composite filmscontaining 5% wt TiO₂. The results are reported in Table 5. TABLE 5 Filmindex of refraction at 1550 nm PMMA (two sample films) 1.479, 1.479PMMA + TiO₂ from Example 4 1.512, 1.514 (two composite sample films)

Comparative Example F

This example shows that reaction of ZrOCl₂.8H₂O with NH₄OH in water doesnot result in calcined ZrO₂ as obtained via aqueous saturated NH₄Clsolution.

11.0 g ZrOCl₂.8H₂O were dissolved in 100 mL deionized H₂O while stirringwith a Teflon coated magnetic stirring bar in a 250 mL Pyrex beaker.With stirring, 10 mL concentrated NH₄OH were added to the zirconiumsolution. The pH of the slurry, measured with multi-color strip pHpaper, was about 10. The resulting slurry was stirred for 60 minutes atambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina crucible and heateduncovered from room temperature to 450° C. over the period of one hour,and held at 450° C. for an additional hour. The crucible and itscontents were removed from the furnace and cooled naturally to roomtemperature.

An X-ray powder diffraction pattern of the calcined material showed amixture of the monoclinic and tetragonal forms of ZrO₂ with thecrystallites ranging 11-16 nm in size. Nitrogen porosimetry revealed asurface area of 63.4 m²/g, a pore volume of 0.13 cc/g, and an averagepore diameter of 84 Å. The porosimetry data of this Example are reportedin Table 6.

Example 15

This example, using ZrOCl₂.8H₂O in aqueous saturated NH₄Cl solution,illustrates the synthesis of calcined ZrO₂ product in accordance withthis invention.

11.0 g ZrOCl₂.8H₂O were dissolved in 100 mL aqueous NH₄Cl solutionsaturated at room temperature, while stirring with a Teflon coatedmagnetic stirring bar in a 250 mL Pyrex beaker. With stirring, 20 mL 1:1NH₄OH:H₂O were added to the zirconium solution. The pH of the slurry,measured with multi-color strip pH paper, was about 10. The resultingslurry was stirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina crucible and heateduncovered from room temperature to 450° C. over the period of one hour,and held at 450° C. for an additional hour. The crucible and itscontents were removed from the furnace and cooled naturally to roomtemperature.

An X-ray powder diffraction pattern of the calcined material showed onlythe tetragonal form of ZrO₂ with 7 nm crystals. Nitrogen porosimetryrevealed a surface area of 84 m²/g, a pore volume of 0.31 cc/g, and anaverage pore diameter of 146 Å. The porosimetry data of this Example arereported in Table 6.

Example 16

This example, using ZrOCl₂.8H₂O illustrates the synthesis of calcinedproduct via addition of NH₄Cl after forming the ZrO₂ precipitate. 11.0 gZrOCl₂.8H₂O were dissolved in 100 mL deionized H₂O at room temperaturewhile stirring with a Teflon coated magnetic stirring bar in a 250 mLPyrex beaker. With stirring, 10 mL concentrated NH₄OH were added to thezirconium solution. After a few minutes, 45 g NH₄Cl were added to theslurry, and the mixture was stirred for 60 minutes at ambienttemperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina crucible and heateduncovered from room temperature to 450° C. over the period of one hour,and held at 450° C. for an additional hour. The crucible and itscontents were removed from the furnace and cooled naturally to roomtemperature.

An X-ray powder diffraction pattern of the calcined material showed onlythe tetragonal form of ZrO₂ with 7 nm crystals. Nitrogen porosimetryrevealed a surface area of 81.5 m²/g, a pore volume of 0.38 cc/g, and anaverage pore diameter of 187 Å. The porosimetry data of this Example arereported in Table 6.

Comparative Example G

Reaction of HfOCl₂.8H₂O with NH₄OH in water does not give HfO₂,calcined, as obtained via aqueous saturated NH₄Cl solution. 10.0 gHfOCl₂.8H₂O were dissolved in 200 mL deionized H₂O while stirring with aTeflon coated magnetic stirring bar in a 250 mL Pyrex beaker. Withstirring, 3.5 mL concentrated NH₄OH were added to the hafnium solution.The pH of the slurry, measured with multi-color strip pH paper, wasabout 8-9. The resulting slurry was stirred for 60 minutes at ambienttemperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina crucible and heateduncovered from room temperature to 450° C. over the period of one hour,and held at 450° C. for an additional hour. The crucible and itscontents were removed from the furnace and cooled naturally to roomtemperature.

An X-ray powder diffraction pattern of the calcined material showed itto be amorphous. Nitrogen porosimetry revealed a surface area of 62.5m²/g, a pore volume of 0.05 cc/g, and an average pore diameter of 29 Å.The porosimetry data of this Example are reported in Table 6.

Example 17

This example, using HfOCl₂.8H₂O in aqueous saturated NH₄Cl solution,illustrates the synthesis of calcined HfO₂ product.

10.0 g HfOCl₂.8H₂O were dissolved in 200 mL aqueous NH₄Cl solutionsaturated at room temperature, while stirring with a Teflon coatedmagnetic stirring bar in a 250 mL Pyrex beaker. With stirring, 3.5 mLconcentrated NH₄OH were added to the hafnium solution. The pH of theslurry, measured with multi-color strip pH paper, was about 8. Theresulting slurry was stirred for 60 minutes at ambient temperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina crucible and heateduncovered from room temperature to 450° C. over the period of one hour,and held at 450° C. for an additional hour. The crucible and itscontents were removed from the furnace and cooled naturally to roomtemperature.

An X-ray powder diffraction pattern of the calcined material showed onlythe monoclinic form of HfO₂ with crystallites approximately 8-11 nm insize. Nitrogen porosimetry revealed a surface area of 49.9 m²/g, a porevolume of 0.20 cc/g, and an average pore diameter of 161 Å. Theporosimetry data of this Example are reported in Table 6.

Example 18

This example, using HfOCl₂.8H₂O illustrates the synthesis of calcinedproduct via addition of NH₄Cl after forming the HfO₂ precipitate. 10.0 gHfOCl₂.8H₂O were dissolved in 200 mL deionized H₂O at room temperaturewhile stirring with a Teflon coated magnetic stirring bar in a 250 mLPyrex beaker. With stirring, 3.5 mL concentrated NH₄OH were added to thezirconium solution. After a few minutes, 85 g NH₄Cl were added to theslurry, and the mixture was stirred for 60 minutes at ambienttemperature.

The solid was collected by suction filtration and dried under an IR heatlamp. The powder was transferred to an alumina crucible and heateduncovered from room temperature to 450° C. over the period of one hour,and held at 450° C. for an additional hour. The crucible and itscontents were removed from the furnace and cooled naturally to roomtemperature.

An X-ray powder diffraction pattern of the calcined material showed onlythe monoclinic form of HfO₂ with crystallites 8-10 nm in size. Nitrogenporosimetry revealed a surface area of 53.2 m²/g, a pore volume of 0.17cc/g, and an average pore diameter of 130 Å.

The surface area and pore characteristics of the products of theexamples are reported in the following Table 6.

Comparative Example H

This example illustrates how a Y-mixer pumped at a relatively slowsolution/mixture flow rate does not ultimately produce a calcined TiO₂product having the surface area and porosity properties of TiO₂ made byprocesses of this invention.

A 50 wt % solution of TiCl₄ in H₂O (28.0 mL) was added to a saturatedaqueous solution of NH₄Cl (200 mL). This caused precipitation of NH₄Clto make an aqueous slurry. Separately, NH₄OH (30 mL, 14.8 M) was addedto a saturated aqueous solution of NH₄Cl (200 mL). No precipitateformed. The slurry and the solution were each stirred separately usingTeflon®-coated magnetic stirring bars in 500 mL Pyrex® Erlenmeyerflasks. A Cole-Parmer peristaltic pump with two size 16 pump heads andsilicone tubing was used to combine the slurry and the solution in apolypropylene Y-joint with a combined flow rate of approximately 160mL/min., i.e., each stream was pumped at about 80 mL/min. As the twostreams were combined, a white slurry formed. The slurry flowed into abeaker and was stirred using a Teflon®-coated magnetic stirring bar. ThepH of the resulting slurry, measured with multi-color strip pH paper,was about 8.

The solid was collected by vacuum filtration (0.45 μm, Nylon filter) andair dried for several days at room temperature to give a white solid.The solid was then pulverized using a mortar/pestle, transferred to analumina tray, heated uncovered (calcined) in a tube furnace from roomtemperature to 400° C. over the period of 1 h, and held at 400° C. for20 h. The firing was done under a constant air flow to help remove thesublimed NH₄Cl byproduct. The furnace was allowed to cool naturally toroom temperature, and the fired material was recovered.

An X-ray powder diffraction pattern of the calcined material showed apredominance of anatase and traces of rutile and brookite. Nitrogenporosimetry revealed a surface area of 75 m²/g, a pore volume of 0.38cc/g, and an average pore diameter of 201 Å. The porosimetry data ofthis Example are reported in Table 6.

Example 19

This example illustrates how a T-mixer pumped at a relatively fastsolution/mixture flow rate ultimately produces a calcined TiO₂ producthaving high surface area and porosity.

A 50 wt % solution of TiCl₄ in H₂O (56.0 mL) was added to a saturatedaqueous solution of NH₄Cl (400 mL) with stirring in a 600 mL Pyrexbeaker. This caused precipitation of NH₄Cl to make an aqueous slurry.Separately, NH₄OH (60 mL, 14.8 M) was added to a saturated aqueoussolution of NH₄Cl (400 mL) with stirring in a 600 mL Pyrex beaker. Noprecipitate formed. The slurry and the solution were each rapidlystirred, separately, using Teflon®-coated magnetic stirring bars. Twoseparate identical Cole-Parmer Masterflex® L/S® peristaltic pumps, eachfitted with 0.19 inch inner diameter silicone tubing, were used tocombine the slurry and the solution, respectively, in a polypropyleneT-joint at a combined flow rate of approximately 2000 mL/min, i.e., eachstream was pumped at about 1000 mL/min. As the two streams combined, awhite slurry formed. The slurry was directed into a 1 L glass bottleequipped with a polypropylene-coated steel stirring blade whose speedwas controlled by an overhead motor. The stirrer speed was adjusted tokeep the slurry rapidly mixed. The pH of the resulting slurry, measuredwith multi-color strip pH paper, was about 8.

The solid was collected by vacuum filtration (0.45 μm, Nylon filter) anddried under an IR heat lamp overnight. The solid was then pulverizedusing a mortar/pestle, transferred to an alumina tray, heated uncovered(calcined) in a tube furnace from room temperature to about 450° C. overthe period of 1 h, and held at 450° C. for 1 h. The firing was doneunder a constant air flow to help remove the sublimed NH₄Cl porogen. Thefurnace was allowed to cool naturally to room temperature, and the firedmaterial was recovered.

An X-ray powder diffraction pattern of the calcined material showed apredominance of anatase and a small amount of rutile. The amount ofanatase was estimated to be about 95% by comparing the observedintensity of the strongest diffraction line for anatase with theobserved intensity of the strongest diffraction line of rutile. Nitrogenporosimetry revealed a surface area of 93 m²/g, a pore volume of 0.56cc/g, and an average pore diameter of 239 Å. The porosimetry data ofthis Example are reported in Table 6. TABLE 6 Ave. Pore Pore SurfaceArea, Vol. Diam. Example Material m²/g (cc/g) (Å) Comparative Auncalcined TiO₂ 398 0.37 37 Comparative A calcined 72 0.17 95Comparative B uncalcined 215 0.17 31 Comparative B calcined 70 0.25 146Comparative C 75.8 0.24 129 Comparative D-I 82 0.4 193 Comparative D-II74 0.37 202 Comparative D-III 109 0.28 105  1 88 0.72 325  2 84 0.78 371 3 89 0.65 293  4 86 0.93 435  5 91 0.63 276  6 89 0.56 251  7 78 0.74378  8 88 0.68 313  9 80 0.52 260 10 511 0.86 68 Comparative E 61 0.34223 11 526 0.47 35 Comparative F ZrO₂ 63.4 0.13 84 15 84 0.31 146 1681.5 0.38 187 Comparative G HfO₂ 62.5 0.05 29 17 49.9 0.20 161 18 53.20.17 130 Comparative H TiO₂ 75 0.38 201 19 93 0.56 239

The data of table 6 show that this invention provides mesoporousproducts having high surface areas and high pore volumes and highaverage pore diameters. While the surface area of the uncalcinedtitanium-containing product of Comparative Examples A and B was high itwas not as high as the uncalcined product of Example 10. Also, the porevolume and average pore diameter of the uncalcined product ofComparative Examples A and B was lower than that of titanium-containingproduct of Example 10.

While the surface area of the calcined product of Comparative ExampleD-II was higher than that of Examples 1-9 the pore volume and averagepore diameter of the calcined product of Comparative Example D-III wasmuch lower than that of the calcined product of Examples 1-9. Moreover,while the surface area of the product of example D-I was slightly higherthan Examples 7 and 9, the pore volume and average pore diameter werelower.

1. A process for making a mesoporous oxide of titanium, comprising:precipitating an ionic porogen and a hydrolyzed compound comprisingtitanium; and removing the ionic porogen from the precipitate to recovera mesoporous oxide of titanium, the amount of ionic porogen and theprecipitating conditions being effective for producing a mesoporousoxide of titanium having a pore volume of at least about 0.5 cc/g and anaverage pore diameter of at least about 200 Å.
 2. The process of claim 1wherein the ionic porogen is a halide salt.
 3. The process of claim 1wherein the ionic porogen is ammonium chloride.
 4. The process of claim2 wherein the halide salt is ammonium halide, tetramethyl ammoniumhalide or tetraethyl ammonium halide or mixtures thereof.
 5. The processof claim 1 wherein the ionic porogen is removed by calcining.
 6. Theprocess of claim 1 wherein the mesoporous oxide is crystalline.
 7. Theprocess of claim 1 wherein the oxide of titanium further comprises adopant.
 8. The process of claim 1 wherein the hydrolyzed compoundcomprising titanium is derived from titanium tetrachloride, titaniumoxychloride or mixture thereof.
 9. The process of claim 1 wherein atleast 2 moles of the ionic porogen precipitates for each mole of thehydrolyzed compound comprising titanium that precipitates.
 10. Theprocess of claim 8 wherein the ionic porogen is a halide salt and atleast 3 moles of the halide salt precipitates for each mole of thehydrolyzed compound comprising titanium that precipitates.
 11. Theprocess of claim 8 wherein the ionic porogen is a halide salt and atleast 4 moles of the halide salt precipitates for each mole of thehydrolyzed compound comprising titanium that precipitates.
 12. A processfor making a mesoporous oxide of titanium, comprising: precipitating anionic porogen and a hydrous oxide of titanium from a reaction mixturecomprising a titanium starting material, a base and a solvent, whereinthe titanium starting material or the solvent, or both, are a source ofthe anion for the ionic porogen and the base is the source of the cationfor the ionic porogen, the precipitating being carried out underconditions effective for recovering a mesoporous oxide of titaniumhaving a pore volume of at least about 0.5 cc/g and an average porediameter of at least about 200 Å after removing the ionic porogen fromthe precipitate.
 13. The process of claim 12 wherein the ionic porogenis a halide salt.
 14. The process of claim 12 wherein the ionic porogenis ammonium chloride.
 15. The process of claim 13 wherein the halidesalt is ammonium halide, tetramethyl ammonium halide or tetraethylammonium halide or mixture thereof.
 16. The process of claim 12 whereinthe ionic porogen is removed by calcining.
 17. The process of claim 12wherein the mesoporous oxide is crystalline.
 18. The process of claim 12wherein the oxide of titanium further comprises a dopant.
 19. Theprocess of claim 12 wherein the titanium starting material is titaniumtetrachloride, titanium oxychloride, or mixture thereof.
 20. The processof claim 12 wherein the base is ammonium hydroxide, ammonium carbonate,ammonium bicarbonate, tetramethyl ammonium hydroxide or tetraethylammonium hydroxide or mixture thereof.
 21. The process of claim 12wherein the solvent is ethanol, n-propanol, i-propanol, dimethylacetamide, alcoholic ammonium halide and aqueous ammonium halide ormixture thereof.
 22. The process of claim 12 wherein the reactionmixture is formed by the steps, in order, of contacting the base and thesolvent to form a solution or a mixture and adding the titanium startingmaterial to the solution or mixture.
 23. The process of claim 12 whereinthe reaction mixture is formed by contacting the titanium startingmaterial and the solvent to form a solution or a mixture and adding thebase to the solution or mixture.
 24. The process of claim 13 whereinmore than about 50 weight percent of the halide salt precipitates fromthe reaction mixture, the weight percent based on the total amount ofthe halide salt that can form from the reaction mixture.
 25. The processof claim 19 wherein the ionic porogen is a halide salt and more thanabout 70 weight percent of the halide salt precipitates from thereaction mixture, the weight percent based on the total amount of thehalide salt that can form from the reaction mixture.
 26. The process ofclaim 19 wherein the ionic porogen is a halide salt and more than about90 weight percent of the halide salt precipitates from the reactionmixture, the weight percent based on the total amount of the halide saltthat can form from the reaction mixture.
 27. A process for making amesoporous oxide of titanium, the process comprising: forming a mixtureof a solid hydrolyzed starting material comprising titanium and a liquidmedium; adding a sufficient quantity of a halide salt to the mixture tosaturate the liquid medium of the mixture; recovering the solid from thesaturated liquid medium, the solid comprising a hydrolyzed intermediatecomprising titanium having pores containing the saturated liquid medium;and removing the saturated liquid medium from the solid to recover amesoporous oxide of titanium having a pore volume of at least about 0.5cc/g and an average pore diameter of at least about 200 Å.
 28. Theprocess of claim 27 wherein the liquid medium is the liquid portion ofthe mixture which comprises a solvent.
 29. The process of claim 27wherein the liquid medium comprises a dissolved salt.
 30. The process ofclaim 28 wherein the solvent is ethanol, n-propanol, i-propanol,dimethyl acetamide, alcoholic ammonium halide and aqueous ammoniumhalide or mixture thereof.
 31. The process of claim 27 wherein thehalide salt is ammonium halide, tetramethyl ammonium halide ortetraethyl ammonium halide or mixture thereof.
 32. The process of claim27 wherein the halide salt is ammonium chloride.
 33. The process ofclaim 27 wherein the step of removing the saturated liquid mediumcomprises drying and calcining.
 34. The process of claim 27 wherein themesoporous oxide is crystalline.
 35. The process of claim 27 wherein thehydrolyzed starting material comprising titanium is derived fromtitanium tetrachloride, titanium oxychloride or a mixture thereof.
 36. Acomposition of matter comprising mesoporous oxide of titanium having amicrostructure characterized by a surface area of at least about 70m²/g, a pore volume of least about 0.5 cc/g, and an average porediameter of least about 200 Å.
 37. The composition of matter of claim 36further comprising a treatment with silica, alumina or both.
 38. Aprotective coating composition comprising the oxide of titanium of claim37.
 39. The composition of matter of claim 36 further comprising atreatment with an organic coating agent.
 40. A thermoplastic compositioncomprising the oxide of titanium of claim
 39. 41. A catalyst compositioncomprising the composition of matter of claim
 36. 42. A nanoparticleprecursor comprising the composition of matter of claim
 36. 43. Anoptical device comprising the composition of matter of claim
 36. 44. Aphotovoltaic cell comprising the composition of matter of claim
 36. 45.A lithium battery anode comprising the composition of matter of claim36.